Human embryonic stem cell derivation: influences and origin

Human embryonic stem cells (hESC) have two unique properties: self-renewal and pluripotency. This means that they can be cultured indefinitely in their unspecialized state and can be prompted to differentiate into any of the specialized cells that comprise the human body. The standard method for deriving hESC relies on blastocyst stage embryos with a defined inner cell mass (ICM). These embryos are created for the purposes of infertility treatment and can be donated either due to poor quality or because the patients no longer wish to use them for pregnancy attempts. The success of assisted reproductive technology (ART) treatment is influenced by the quality of the embryos created and by specific patient and cycle variables. Although successful hESC derivation is a direct result of embryo viability, the prognostic values used to predict ART success have not been applied to hESC generation. In addition, the key events that occur during the initial stages of hESC derivation have not been defined. Bridging the gap between the embryology laboratory and the stem cell laboratory is needed to better understand what influences the success of hESC derivation and the events that underlie hESC generation.
In this thesis we determined that embryos with poor quality traits are an abundant and viable source for establishing new hESC lines. As such, they can be used experimentally to improve hESC derivation efficiency, to optimize derivation in defined culture conditions, and to better understand the origins of human pluripotency. Importantly, our data have shown that poor quality embryos are a heterogeneous population with varying levels of developmental potential. Embryos showing two or more poor quality traits were not able to support hESC derivation. We determined that the prognostic variables used to predict pregnancy outcome during ART can also be used to predict successful hESC derivation. Poor quality embryos originating from older patients (>37y) showed impaired embryonic developmental potential and failure to generate hESC lines. Since good quality ICM were not equal in their ability to generate hESC, understanding the patient and cohort parameters of the embryos comprising the PQE pool can help predict hESC derivation efficiency and aid in establishing experimental groups with equal developmental competence.
We also investigated the temporal and cellular events that immediately precede primary hESC outgrowth for better insight into their pluripotent state and origin. We identified a distinct pattern of ICM organization that is predictive of hESC outgrowth. This organization culminates in the formation of a post-ICM intermediate structure, termed here as the PICMI, that we showed to be the closest pluripotent progenitor of hESC. By comparing the PICMI to both ICM and hESC, we have determined the extent of in vitro ICM progression towards epiblast and the unique state of cell signalling that initiates hESC outgrowth. These newfound data put the origin and state of existing hESC in a completely new light.

@phdthesis{4098148,
abstract = {Human embryonic stem cells (hESC) have two unique properties: self-renewal and pluripotency. This means that they can be cultured indefinitely in their unspecialized state and can be prompted to differentiate into any of the specialized cells that comprise the human body. The standard method for deriving hESC relies on blastocyst stage embryos with a defined inner cell mass (ICM). These embryos are created for the purposes of infertility treatment and can be donated either due to poor quality or because the patients no longer wish to use them for pregnancy attempts. The success of assisted reproductive technology (ART) treatment is influenced by the quality of the embryos created and by specific patient and cycle variables. Although successful hESC derivation is a direct result of embryo viability, the prognostic values used to predict ART success have not been applied to hESC generation. In addition, the key events that occur during the initial stages of hESC derivation have not been defined. Bridging the gap between the embryology laboratory and the stem cell laboratory is needed to better understand what influences the success of hESC derivation and the events that underlie hESC generation.
In this thesis we determined that embryos with poor quality traits are an abundant and viable source for establishing new hESC lines. As such, they can be used experimentally to improve hESC derivation efficiency, to optimize derivation in defined culture conditions, and to better understand the origins of human pluripotency. Importantly, our data have shown that poor quality embryos are a heterogeneous population with varying levels of developmental potential. Embryos showing two or more poor quality traits were not able to support hESC derivation. We determined that the prognostic variables used to predict pregnancy outcome during ART can also be used to predict successful hESC derivation. Poor quality embryos originating from older patients ({\textrangle}37y) showed impaired embryonic developmental potential and failure to generate hESC lines. Since good quality ICM were not equal in their ability to generate hESC, understanding the patient and cohort parameters of the embryos comprising the PQE pool can help predict hESC derivation efficiency and aid in establishing experimental groups with equal developmental competence.
We also investigated the temporal and cellular events that immediately precede primary hESC outgrowth for better insight into their pluripotent state and origin. We identified a distinct pattern of ICM organization that is predictive of hESC outgrowth. This organization culminates in the formation of a post-ICM intermediate structure, termed here as the PICMI, that we showed to be the closest pluripotent progenitor of hESC. By comparing the PICMI to both ICM and hESC, we have determined the extent of in vitro ICM progression towards epiblast and the unique state of cell signalling that initiates hESC outgrowth. These newfound data put the origin and state of existing hESC in a completely new light.},
author = {O'Leary, Thomas},
language = {eng},
pages = {134},
publisher = {Ghent University. Faculty of Medicine and Health Sciences},
school = {Ghent University},
title = {Human embryonic stem cell derivation: influences and origin},
year = {2012},
}